Design,synthesis And Photoelectric Properties Of Blue Iridium(?) Complexes Based On 2',6'-Difluoro-2,3'-bipyridine Ligand Derivatives

Iridium(?) complexes have attracted a lot of attention in recent years because of their high efficiency,color tenability and nearly 100% internal quantum efficiency.The small molecules based on Iridium(?) complexes are mainly processed by evaporation,this method waste material seriously and not conducive to prepare large-area OLED and reduce costs.Dendrons are introduced into the Iridium(?) complexes,not only effectively suppress the triplet annihilation,but also give the Iridium(?) complexes good solubility and favourable film-forming property,so phosphorescent OLED can be prepared by solution method or inkjet printing.The introduction of dendrons into the Iridium(?) complexes can effectively inhibit the intermolecular interactions,can also improve the photoelectric properties.Compared to 2-(2,4-difluorophenyl)pyridine(dfppy)mian ligand,2',6'-difluoro-2,3'-bipyridyl(difluoro pyridine,dfpypy)has a higher triplet energy level and is an excellent blue phosphorescent ligand.The dendron group based on alkoxy group on trimethylbenzene is introduced into the ligand unit of the dfpypy,so that the Iridium(?) complexes have good solubility and film-forming property and phosphorescent OLED can be prepared by solution method or inkjet printing.Details are as follows:(1)Three small blue Iridium(?) complexes based on the dfpypy as main ligand and the triazoles as ancillary ligands were designed and synthesized.The triazole-based ancillary ligands can form stable complexes,and different numbers of fluorine atoms can be introduced on the triazole ligands to investigate the effects of different fluorine atom numbers on the properties of the ruthenium complexes.After studying the thermal stability,electrical properties and optical properties,the relationship between structure and performance was explored.As the fluorine atoms on the ancillary ligands increased,they can effectively make the spectrum bluer without changing the quantum efficiency.(2)A series of blue Iridium(?) complexes based on the dfpypy derivatives were designed and synthesized.In the study of the photophysics properties,we found that the dendrimer was introduced into the pyridine ring of the dfpypy,which weakened the intermolecular quenching of the complex and enhanced the quantum efficiency.At the same time,the dendrimer can also improve the thermal stability,film formation and transient luminescence lifetime of Iridium(?) complexes.We have found that the introduction of the dendrimer not only unchange the peak emission of the Iridium(?) complexes,but also improve the OLED performance.DIr-dpm-doped blue OLED exhibited the highest performance,achieving the maximum luminous efficiency(LE)of 19.8 cd/A and the external quantum efficiency(EQE)of 9.84%.(3)Two monomers based on exo-5-norbornenecarboxylic acid were designed and synthesized and polymers were obtained by the Ring-Opening Metathesis Polymerization(ROMP)method.The effects of dendron on the properties of polymers and small molecules were studied by comparing the properties of small molecule Iridium(?) complexes with the dendritic Iridium(?) complexes,and dendritic Iridium(?) complexes and polymers.We have found that polymers exhibite very high thermal stability than small molecules,for example,the value of the TGA of DIr-P is 391? and the value of the TGA of DIr-M is 300?.Meanwhile,the solution-processed blue OLED device obtained satisfying device performance and we also attempted to made blue phosphorescent OLED by inkjet printing.(4)Design and synthesis of main ligand based on the Phenyl alkoxy chain,using cyano,pyridine,2,2'-dipyridine and other electron-withdrawing groups as ancillary ligands to prepare deep-blue ionic Iridium(?) complexes.By studying its lifetime,photophysical properties,quantum efficiency,thermal stability and OLED device performance,we studied the effects of different electronwithdrawing groups on the properties of Iridium(?) complexes.Iridium(?) complexes Ir-Py based on pyridine ancillary ligand can obtained good device efficiency,achieving a maximum luminous efficiency(LE)of 5.36 cd/A and external quantum efficiency(EQE)of 2.35%.